Cost to start up Biz

I have all my equipment already. I have been mowing, trimming aerating for about 20 res. clients this past year and doing snow in the winter. I grossed around $10k. I want to be fully legit as soon as possible and i dont know if that is 18 or not but i want to go after commercial accounts and carry insurance.
My questions are:
How much is it to register a business name, get liabily, insurance up to i guess 1mil.
Employees will be my brothers and I only.
How much will starting this bus. cost me?
I plan on buying an enclosed trailer and plastering our name all over it, get business cards, send out approx 2000 flyers to upscale neighborhoods, door hangers on new homes, put in a few bids around me, and ask for extra work from local lcos that i know. Is this logical for me to do right now?